1. Field of the Invention
The present invention relates to a portable support structure, possibly foldable, able to be used as a ladder or stepladder to enable a person to move, especially going up or down, for example to reach objects otherwise inaccessible or for getting past obstacles.
2. Description of the Prior Art
Generally speaking, it is known that conventional ladders are made up of two parallel or slightly convergent stanchions recombined from place to place by transversal bars or ladder rungs used as steps.
At one of their extremities, these stanchions have support surfaces on the ground and possibly equipped with bolsters. The two other extremities of the stanchions are intended to rest on a support surface, such as on a vertical wall (case of a simple ladder) or are joined to a support structure able to consist of a second ladder (case of double ladder).
In the case of a double ladder, the stanchions constitute shafts bearing steps instead of rungs. In this case, the support structure includes two parallel stanchions connected together by crosspieces and to the shafts by disconnectable bracing means.
Generally speaking, so as to ensure his balance, the user mounted on a ladder is often obliged to keep one hand on the bars or on the stanchion and thus is not fully free to move as he would like. This drawback is particularly prejudicial when the user has to carry out works, such as painting work requiring the simultaneous use of both hands.
Another problem put forward by conventional solutions concerns the a stability of the ladder and the risk of the user falling, it being understood that this stability can only be attained if the vertical projection of the centre of gravity of the user and/or the ladder occurs inside the support polygon of the ladder, that is a polygon formed by the vertical projection inside a horizontal plane of the support points of the ladder.
Now the dimensions of this support polygon vary according to the location of the support points of the ladder, whereas there is nothing enabling the user to indicate the position of his centre of gravity with respect to this polygon.
Thus, the user can find himself out of balance and fall without receiving any sign warning him of this danger.
This drawback is clearly shown in the case of double ladders or stepladders which comprise four support points on the ground. Having regard to the irregularities of the shape of the ground, the ladder or stepladder in fact most often only rests on three legs which considerably reduces the dimensions of the support polygon. In addition, the verticality of the ladder or stepladder is relatively difficult to obtain which further increases the risks of falling.
Thus, the main object of the invention is to eliminate these drawbacks and resolve these problems. These results can be attained by using a relatively simple structure able to be easily folded yet being less expensive.
According to the invention, this structure includes at least:
a shaft whose two extremities are intended to come into support on two fixed elements, one of these elements possibly consisting of the ground and the other a fixed object situated above the ground,
two sets of steps secured to the shaft respectively on both sides of the latter.
According to the invention, this structure is characterised in that one of the extremities of the shaft constitutes one of the support means on the ground, whereas two legs are joined to the other extremity so as to obtain in a deployed state a tripod structure, and in that it comprises a ramp, integral with the shaft and extending to the vertical position of the latter at a distance of steps less than the average length of a leg so that a user is able to move on the steps by straddling the ramp and able to tighten said ramp between his legs so as to stay on the structure without having to use his hands which remain free for carrying out work operations.
At the same time, this double support on the ramp tends to bring the user back into a vertical plane in a position where he benefits from having better stability.
Advantageously, the steps could include means for the lateral side locking of the legs so as to ensure improved structure/user integration when the user tightly holds the ramp between his legs.